Can an acid pit be mined for valuable metals before it rises too high?

In its raucous heyday 80 years ago, this Montana mining town was known as the richest hill on earth. Its rocky soil yielded millions of tons of copper ore, used to make the wires that spread power and light and phones across the nation. Then, 16 years ago, the giant strip mine was closed, and the pumps that kept it dry were turned off for good.

Ever since, waters from the surrounding bedrock and a maze of old mine tunnels and shafts have been rushing in and reacting with the ores to form a toxic soup that rises steadily, year after...